When food products kept in a refrigerated self serve merchandiser have to remain visible for the consumers, as is the case in numerous commercial premises at the present time, the refrigerated merchandiser is preferably equipped with transparent glazing unit in order to save energy costs. These refrigerated self serve merchandisers exist in many various forms. When these merchandisers are vertical, then it is the door itself which contains the transparent glazing unit. When these merchandisers are horizontal and constitute chests, then it is the horizontal lid door which contains the transparent glazing unit to allow the contents to be seen. The refrigerated merchandiser is also commonly referred to as a refrigerated display case.
In these types of merchandisers, it is necessary that the food products remain easily visible to the customers so that the products can be preselected without opening the merchandiser.
However, one of the main problems encountered with these merchandisers is the condensation that builds up on the exterior surface of the glazing unit facing the ambient atmosphere. What happens is that this exterior surface is cooled by the refrigerated environment on the opposite side of the glazing unit. When the temperature of this exterior surface is at a temperature below the dew point, visible condensation occurs in form of droplets, which makes the food products on display barely visible.
Another significant problem is the formation of visible condensation, or even frost, on the interior surface of the glazing unit when the door of the display case is opened in order to take the food products out. What happens is that the inside surface of the glazing unit, which is at a very low temperature, often times below 0° C., contacts the ambient atmosphere, which is far more loaded with moisture and at a far higher temperature. The temperature of this interior surface is usually then below the dew point, which causes visible condensation to form on the surface. This condensation can even turn to frost when the temperature of this surface is below 0° C. or 32° F. The presence of condensation or frost makes a visible barrier between the consumers and the food products, and it then takes several minutes or even several tens of minutes, for this condensation or the frost to completely disappear. When the food products are not easily visible, impulse sales are lost and customers open the doors for longer periods of time to select the food products, which causes the refrigeration unit to run longer to maintain the temperature of the goods and generates at the same time more condensation or frost that will require more time to disappear.
The use of performing insulating glazing units in refrigerated display cases has been avoided since it exacerbates the problem of condensation or frost forming on the surface of the glazing unit facing the interior of the merchandiser. When the insulation is performing, then the inside surface is cooler and the cooler the surface the greater the problem of condensation or frosting when the door is opened.
Heating means are commonly used to reduce the problem of condensation or 0 frost forming on the surface of the glazing unit facing the interior of the merchandiser. See, for example, U.S. Pat. Nos. 5,449,885, 5,852,284, and 6,144,017, which all disclose the use of heating means. However, the use of heating means consumes significant quantities of electricity, first to generate the heat and second to compensate through the refrigeration unit for the heat that is transferred inside the merchandiser. And despite this, depending on the ambient conditions and the power of these heated means, condensation or frost can still occur and the benefit of the heated means is then only to rapidly remove condensation or frost in a short period (generally less than 2 minutes).
Furthermore, while the use of insulating glazing units in combination with heating means has been disclosed in these patents, the various functional layers used previously, including the low-emission coatings, disclosed in these patents substantially reduce the light transmission ratios of the glazing units so that additional lighting power is often required inside the merchandiser to compensate and to see the food products on display. This additional lighting generates additional heat, which can increase the temperature of the products on display in the merchandiser and requires additional power consumption by the corresponding refrigeration unit.
In light of rising energy costs, there is a great need for an environmentally friendly refrigerated merchandiser having an insulating transparent glazing unit that does not require powerful interior lighting or heating means to avoid visible condensation or frost formation on the exposed surfaces of the glazing unit.